The present invention relates to a control process with temporally cyclically controlled determination of manipulated variables from primary input values (actual values) in accordance with a fuzzy logic, in which the manipulated variables act on the controlled system in the sense of a reduction of a theoretical/actual deviation.
Such a process is disclosed, by way of example, in the article "Fuzzy Control--heuristic control by means of fuzzy logic", which appears in the German journal "Automatisierungstechnische Praxis" ATP 4/1992, pages 176-183 and 5/1992, pages 239-246. In the article, the general mode of operation of fuzzy controllers is described. Furthermore, the various control characteristics are established.
In order to permit a rapid reaction by the controller to a defect which has occurred, controllers are known from the conventional control technology that exhibit a differentiation component (D-component). Differential control behavior is, by definition, only a reaction to an alteration of the primary input variable. Fuzzy controllers of themselves do not possess any such D-component. By appropriate choice of the determinable parameters of the fuzzy controller, it is possible, as described in the article, to approximate a differential controller behavior.
The object of the invention is to improve the control process which forms the basis of the type discussed above so that an improved reaction to changes to the input variable is permitted.
This and other objects are achieved by the present invention which provides a control process with temporally cyclically controlled determination of manipulated variables of a controlled system from primary input variables representing actual values in accordance with a fuzzy logic. The manipulated variables act on the controlled system to reduce a theoretical or actual deviation. The control process comprises the steps of determining a fictitious input variable of a next following cycle from a primary input variable of a last past cycle and the primary input variable of a current cycle; and determining the manipulated variable according to the fuzzy logic, including the step of implying at least the determined fictitious primary input variable cycle in the determination of the manipulated variable.
By the determination of the fictitious, probable input variable of the next following cycle and consideration of this value in the determination of the manipulated variable, account is taken of a probable development of the input variable and appropriate action is taken in advance on the manipulated variable. The consideration of an extrapolated future, fictitious input variable value is possible, since control loops with fuzzy controllers are not inclined to show a resonance behavior between a control variable and a manipulated variable, as usual with conventional controlled systems.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.